Does somatostatin confer insulinostatic effects of neuromedin u in the rat pancreas?
OBJECTIVE
Neuromedin U (NmU) is a neuropeptide with anorexigenic activity. Two receptor subtypes (NmUR1 and NmUR2) confer the effects of NmU on target cells. We have recently demonstrated that NmU reduces insulin secretion from isolated pancreatic islets. Aim of our current study is to investigate the role of somatostatin at mediating the effects of NmU on insulin secretion.


METHODS
Expression of NmU in the pancreas was detected by immunohistochemistry. Insulin and somatostatin secretion from in situ perfused rat pancreas and isolated pancreatic islets was measured by radioimmunoassay. The paracrine effects of somatostatin within pancreatic islets were blocked by cyclosomatostatin, a somatostatin receptor antagonist.


RESULTS
Receptor subtype NmUR1, but not NmUR2, was expressed in the endocrine pancreas, predominantly in the periphery. Neuromedin U reduced insulin secretion from in situ perfused rat pancreas and stimulated somatostatin secretion from isolated pancreatic islets. Neuromedin U stimulated somatostatin secretion at both physiological and supraphysiological glucose concentrations. Cyclosomatostatin increased insulin secretion and reduced NmU-induced inhibition of insulin secretion.


CONCLUSIONS
Neuromedin U reduces insulin and increases somatostatin secretion. Blockade of somatostatin action abolishes the inhibition of insulin secretion by NmU. The results of the study suggest that somatostatin mediates the inhibitory action of NmU on insulin secretion.
Kaczmarek
Przemyslaw
P
Department of Animal Physiology and Biochemistry, August Cieszkowski University of Agriculture, Poznan, Poland.
Malendowicz
Ludwik K
LK
Fabis
Marzena
M
Ziolkowska
Agnieszka
A
Pruszynska-Oszmalek
Ewa
E
Sassek
Maciej
M
Wojciechowicz
Tatiana
T
Szczepankiewicz
Dawid
D
Andralojc
Karolina
K
Szkudelski
Tomasz
T
Strowski
Mathias Z
MZ
Nowak
Krzysztof W
KW
D000818:Animals; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D009479:Neuropeptides / Q000494:pharmacology*; D010179:Pancreas / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017981:Receptors, Neurotransmitter / Q000032:analysis / Q000502:physiology; D013004:Somatostatin / Q000502:physiology*
D007328:Insulin; D009479:Neuropeptides; D017981:Receptors, Neurotransmitter; C082444:neuromedin U receptor; C056900:neuromedin U; D013004:Somatostatin